Along with the downsizing of hybrid vehicles or electric vehicles, reduction in size of vehicle parts including power conversion devices used for the vehicles has been required. In this respect, the power conversion device is mounted on a vehicle part such as a transmission or a motor, so that the power conversion device and a case of the transmission or the motor can be integrated together, which can result in a reduction in system cost and downsizing on the whole. In this context, for downsizing of the whole vehicle, there may be a strong demand for a reduction in thickness, in particular.
For an internal structure of the power conversion device, integration of a plurality of circuit substrates in the device is getting attention for a reduction in cost resulting from a reduction in thickness and elimination of harnesses between the substrates. For example, the power conversion device includes a motor control circuit (MC) substrate for motor control by means of onboard microcomputers, and a drive circuit (GD) substrate for ON/OFF control of gates of power switching elements having IGBTs and the like. Since there are a multiplicity of control wirings between the MC substrate and the GD substrate, the trend has been toward integration of the substrates.
However, in conventional power conversion devices, if a noise of high voltage side switching parts (a power module, AC bus bars, the GD substrate) enters into the MC substrate in a low voltage side, the switching noise propagating to the MC substrate leaks out of the power conversion device via signal harnesses or the like. This electromagnetic noise presents a problem. Thus, a metal base plate is arranged between the high voltage switching parts and the MC substrate, i.e. a low voltage part, for example, so that the base plate interrupts the noise between the high voltage switching parts and the MC substrate. However, when the MC substrate and the GD substrate are integrally formed in one substrate, there is a problem of the switching noise propagating from the GD part to a vicinity of the MC part and then leaking out via a connector or the like, which is a case opening part, to the outside.
As an approach of suppressing such a noise propagation, a structure is known that includes a shielding part so as to close the case opening part (connector part), in order to interrupt noise radiation from an electromagnetic wave oscillating part to the outside of the case or noise entry from the outside (see PTL1).